In order to balance supply and demand of an electric power, a control mode for a customer to subjectively meet a request of supply and demand adjustment from an electric power system, which is called a demand-response, is well known. As to the customer having a plurality of home appliances, in order to execute the demand-response, a method for controlling each device with communication is used. Here, a power measurement device having a communication function collects various information (such as a correspondence relationship between operation status and power consumption, a user setting, the present power consumption) from each device (such as an air conditioner, an illumination). When the electric power system generates a request of supply and demand adjustment, in response to this request, the power measurement device transmits an operation control signal to each device.
In this method, in order to cope with variation of combination of various devices and change of component due to addition or deletion of device, the power control device transmits/receives many parameters with each device, determines a plan to adjust the electric power, and transmits a control instruction thereof. In this case, even if the power consumption momentarily rises, the power control device often adjusts the electric power.
However, as to the device actually operating, fixed power consumption is not always maintained in a certain operation status. Briefly, it often happens that the power consumption momentarily rises. In this case, when a usable electric power is below a threshold, even if the usable electric power is above the threshold at a next moment, adjustment of the electric power is performed. Here, a method for returning the electric power to a original status thereof is same as a method for controlling congestion. Accordingly, after adjustment of the electric power is performed once, comfortableness is damaged for a while.